formatter: provide hint of context keys required by template
This allows us to create ctx objects only if necessary.
I tried another idea which is to populate ctx from 'repo' and 'node' value
on demand. It worked, but seemed unnecessarily complicated. So I chose a
simpler one.
The datafields argument is a space-separated string for consistency with
fm.write() API.
BasedOnStyle: LLVM
IndentWidth: 8
UseTab: ForIndentation
BreakBeforeBraces: Linux
AllowShortIfStatementsOnASingleLine: false
IndentCaseLabels: false
AllowShortBlocksOnASingleLine: false
AllowShortFunctionsOnASingleLine: false
IncludeCategories:
- Regex: '^<'
Priority: 1
- Regex: '^"'
Priority: 2